I've always wondered if the possibility of restraining the massive operations in the Pacific theater in light of the approaching reality of nuclear warfare was ever considered. As I understand, the islands assaulted by the allies were taken to prepare for an invasion of mainland Japan. Why did the allies expend such excessive resources and troops if they were already working with the nuclear option which could be used to bring Japan to its knees?
With the benefit of hindsight, it's easy to forget that there was not only no way to know when a bomb would be ready, there was no way to know if a bomb would be ready. While the physics penciled out, there was no guarantee that a hypothetical design would function properly.
Moreover, the knowledge of the bomb was limited. Adm. Nimitz didn't learn of it until February 1945 (No High Ground) when planning experts began looking for a place to station the 509th Composite Group.
There was also no way to know that the bomb would be powerful enough to influence a surrender decision.